Active drone detection systems have existed which give away the location of the drone detection system and cost more power to operate. Some other techniques include: (1) audio techniques that require multiple sensors in order to localize the threat, and are susceptible to interference from other noise sources (traffic, aircraft, industrial noise, insect noise, etc.) and are limited in useful range; (2) radar that is an active RF-emitting technique, large, costly, and limited in its ability to detect small largely non-metallic objects such as commercial vehicles; and (3) optical techniques that solely rely on motion or appearance-based object detection, which are susceptible to false alarms from birds, aircraft, and other airborne objects, typically require the drone to be moving rather than hovering in one spot, and cannot reliably identify the object of interest in a cluttered scene.